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Propeller-2 EVAL Board — Parallax Forums

Propeller-2 EVAL Board

JonTitusJonTitus Posts: 193
in Propeller 2
What is the default processor cycle time (frequency) for the Prop-2 IC on the EVAL Board?
Specs indicate a 20-MHz crystal, but measurements here indicate a 25-MHz cycle frequency. I am using the Prop-2 Smart-Pin (%00100 mode) pulse/cycle output mode. A value of 500 for a pulse period works out to a 20-usec pulse duration, so 500 counts/(20*10E-6 sec) = 25*E+6, or 25 MHz. --Jon

Comments

  • JonTitusJonTitus Posts: 193
    I am using the FlexGUI assembly-language compiler for the Prop-2 EVAL Board. Perhaps it defaults code to its own choice of clock frequency?
  • JRoarkJRoark Posts: 1,215
    The processor speed default in FlexBASIC (which I believe is the same default value in all of the supported Flex languages) is 160 mhz on the P2 and 80 mhz on the P1.
  • JonTitusJonTitus Posts: 193
    Neither of which is a multiple of 25 MHz. Hmmm... Perhaps the Smart-Pin configuration for pulses/counts uses operations that rely on a different clock?
  • ersmithersmith Posts: 5,909
    JonTitus wrote: »
    What is the default processor cycle time (frequency) for the Prop-2 IC on the EVAL Board?

    It's not very well defined. When the processor boots it enters "RCFAST" mode, which is nominally 20 MHz but can drift considerably (so it can end up being anything between 20 MHz and 25 MHz; 22 MHz is common, but it sounds like yours is at the high end of the range).

    In practice you'll normally want to use the "hubset" instruction to set a specific operating mode and frequency. Some language runtimes will do this automatically for you, but in assembly language you'll have to issue the hubset yourself.

  • JonTitusJonTitus Posts: 193
    Thanks, ersmith. I appreciate the info about pubset. --Jon
  • Peter JakackiPeter Jakacki Posts: 10,193
    RevB silicon rcfast is typically around 25MHz vs the 22MHz previously I find. So obviously you must be using rcfast.
    Btw, I measured this across many chips by entering TAQOZ ROM, selecting a pin I'm probing, and typing $8000_0000 NCO which sets up the smartpin in NCO mode to output sysclock/2.
  • TubularTubular Posts: 4,621
    Yes I agree 24..26 MHz RCFAST from what I have seen. RCFAST is very stable with respect to temperature.

    RCSLOW on the other hand changes quite a lot with temperature


  • Peter JakackiPeter Jakacki Posts: 10,193
    Tubular wrote: »
    Yes I agree 24..26 MHz RCFAST from what I have seen. RCFAST is very stable with respect to temperature.

    RCSLOW on the other hand changes quite a lot with temperature


    On revB I've found RCSLOW almost always bang-on 20kHz. I even set TAQOZ to 3Mbd @200MHz and then switched to RCSLOW and had it running at 300bd very slowly, and left it like that overnight, no problems. Still works but Really Computes SLOWly
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